Polishing pad

ABSTRACT

A polishing pad generates very few scratches on a surface of a polishing object, and is excellent in planarization property. The polishing pad has a high polishing rate and is excellent in planarization property. The polishing pad grooves become very little clogged with abrasive grains or polishing swarf during polishing and, even when continuously used for a long period of time, the polishing rate is scarcely reduced.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 11/914,547, filed Nov.15, 2007, which is a national stage application under 35 USC 371 ofInternational Application No. PCT/JP2006/309380, filed May 10, 2006,which claims the priority of Japanese Patent Application Nos.2005-144292, 2005-144304 and 2005-144318, each filed May 17, 2005, thecontents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a polishing pad capable of performingplanarization materials requiring a high surface planarity such asoptical materials including a lens and a reflective mirror, a siliconwafer, a glass substrate or an aluminum substrate for a hard disk and aproduct of general metal polishing with stability and a high polishingefficiency. A polishing pad of the invention is preferably employed,especially, in a planarization step of a silicon wafer or a device onwhich an oxide layer or a metal layer has been formed prior to furtherstacking an oxide layer or a metal layer thereon.

BACKGROUND OF THE INVENTION

Typical materials requiring surface flatness at high level include asingle-crystal silicon disk called a silicon wafer for producingsemiconductor integrated circuits (IC, LSI). The surface of the siliconwafer should be flattened highly accurately in a process of producingIC, LSI etc., in order to provide reliable semiconductor connections forvarious coatings used in manufacturing the circuits in each steps ofstacking an oxide layer or metal layer thereon. In the step of polishingfinish, a polishing pad is generally stuck on a rotatable supportingdisk called a platen, while a workpiece such as a semiconductor wafer isstuck on a polishing head. By movement of the two, a relative speed isgenerated between the platen and the polishing head while polishingslurry having abrasive grains is continuously supplied to the polishingpad, to effect polishing processing.

As polishing characteristic of a polishing pad, it is requested that apolishing object is excellent in planarity and in-plane uniformity and apolishing rate is large. A planarity and in-plane uniformity of apolished object can be improved to some extent with a polishing layerhigher in an elastic modulus.

In view of development in next generation elements, a polishing padhaving a higher hardness which can further improve planarity isrequired. In order to improve planarity, it is possible to use anon-foam-based hard polishing pad. However, when such the hard pad isused, there arises a problem that a surface to be polished of apolishing object is scratched. In addition, since the non-foam-basedpolishing pad cannot sufficiently retain abrasive grains in slurry on apad surface at polishing processing, this is not desirable also from aviewpoint of a polishing rate.

In addition, a polishing pad in which a water-soluble material isdispersed in a thermoplastic polymer has been disclosed (Japanese PatentApplication Laid-open (JP-A) No. 2001-47355). Although this polishingpad is a non-foam, since a water-soluble material dispersed in apolishing pad is dissolved at polishing, a pore like a foam is formed ona polishing pad surface, a polishing pad is swollen, and a hardness of apolishing pad surface is reduced, the pad is effective for reducing ascratch and improving a polishing rate. However, since a surface of thepolishing pad is swollen, and a hardness is reduced, planarizationproperty is insufficient.

In addition, for the purpose of realizing both of improvement inplanarity and reduction in scratch, there is disclosed a polishing padcomprising a polymer of an isocyanate-terminal prepolymer obtained byreacting a high-molecular-weight polyol containing an organicpolyisocyanate and a water-soluble polyol and a low molecular polyol,and a chain extender (Japanese Patent No. 3571334). However, since asurface of the polishing pad is swollen, and a hardness is reduced,planarization property required in the future cannot be sufficientlysatisfied.

On the other hand, a polishing rate can be improved by using a foamcontaining pores, thereby, increasing an amount of slurry to beretained.

As a polishing pad satisfying the aforementioned properties, a polishingpad comprising a polyurethane resin foam has been disclosed (JP-A No.2000-17252 and Japanese Patent No. 3359629). The polyurethane resin foamis produced by reacting an isocyanate-terminal prepolymer and a chainextender (curing agent) and, as a high-molecular-weight polyol componentof an isocyanate prepolymer, polyether (particularly polytetramethyleneglycol having a number average molecular weight of 500 to 1600) andpolycarbonate polyol are used as a suitable material, from a viewpointof hydrolysis resistance, elasticity property, and abrasion resistance.

However, when a modulus of a polishing layer is increased (increase in ahardness) for improving planarization property of a polishing pad, aspecific gravity is increased and, as a result, there is a problem thatthe number of pores per unit area is decreased, and a polishing rate isreduced.

In addition, as a method of increasing an amount of slurry to beretained, there is a method of rendering a polishing pad itselfhydrophilic, specifically, (1) a method of introducing a hydrophilicgroup such as a hydroxyl group etc. into a matrix material, and (2) amethod of mixing a matrix material and a hydrophilic material. Forexample, a composition for a polishing pad containing (A) a crosslinkingelastomer and (B) a material having a functional group such as ahydroxyl group etc. is disclosed (JP-A No. 2002-134445). In addition, apolishing equipment obtained by further adding a hydrophilic material,to a material constituting a polishing equipment, or adding ahydrophilic group thereto (modification) is disclosed (JP-A No.2003-11066). In addition, a polishing pad comprising a thermosettingpolymer matrix resin which is hydrophilic, and contains a substantiallywater-insoluble sheet is disclosed (JP-A No. 2002-59358). Further, apolishing pad comprising a polyurethane composition containing aurethane resin obtained by copolymerizing a compound having ahydrophilic group, and containing a hydrophilizing agent is disclosed(JP-A No. 2003-128910).

However, in the (1) method, when a matrix material is polyurethane, ahydrophilic group containing active hydrogen of a hydroxyl group etc. isreacted with an isocyanate group upon synthesis of polyurethane and, asa result, an unreacted polyol component may remain in a material. And,there is a tendency that since this remaining polyol component exertsthe plastic effect, physical property of a polishing pad isdeteriorated. In addition, in the (2) method, it is difficult touniformly mix a hydrophilic material into a matrix material, and apolishing pad having uniform physical property cannot be obtained.

On the other hand, if a polishing rate varies during from immediatelyafter use to completion of use, polishing condition must be adjusted andthere is a problem that a polishing efficiency is worse.

For example, for the purpose of providing a non-foam urethane polishingmaterial which can effectively polish a semiconductor wafer and isexcellent in planarity, there is disclosed a polishing materialcomprising a polishing material composition which comprises anisocyanate-terminal urethane prepolymer and an activehydrogen-containing compound and in which the isocyante-terminalurethane prepolymer is obtained by using, as polyisocyante, aromaticdiisocyante, and using a polyol component consisting of ahigh-molecular-weight polyol and a low-molecular polyol, thelow-molecular polyol in the polyol component being diethylene glycol,1,3-butylene glycol etc. (JP-A No. 2000-17252).

In addition, for the purpose of imparting dressing property to apolishing cloth itself and prolonging a polishing life, a polishingcloth comprising a polyurethane composition and having an abrasionamount by a Taber abrasion test of 150 to 350 mg is disclosed (JP-A No.2001-277101).

However, the polishing material described in JP-A No. 2000-17252comprises a non-foam urethane, and since such the non-foam-basedpolishing material has a low polishing rate, a groove is foamed on apolishing surface, and it is very difficult to stabilize a polishingrate due to local presence of abrasive grains and polishing swarf inslurry. In addition, since the polishing cloth described in JP-A No.2001-277101 is easily abraded, and has a low hardness (due to notuniform pores, and a large pore size), planarity and in-plane uniformityare not sufficient, and a greater change in a polishing rate cannot beavoided.

Further, the previous polishing pad with a groove has a problem that agroove is clogged with abrasive grains or polishing swarf duringpolishing, and a polishing rate is reduced during use.

In addition, Japanese Patent Application National Publication (LaidOpen) No. 2001-513450, Japanese Patent Application National Publication(Laid Open) No. 2001-518852 and Japanese Patent Application NationalPublication (Laid Open) No. 2002-535843 disclose a polishing padcomprising a polishing material having a breaking extension of 500% orlower. However, technical meaningfulness of use of a pressing materialhaving a breaking extension of 500% or lower is not described at all.

SUMMARY OF THE INVENTION

An object of the first invention is to provide a polishing pad whichhardly generates a scratch on a surface of a polishing object, and isexcellent in planarization property. An object of the second inventionis to provide a polishing pad which has a high polishing rate and isexcellent in planarization property. An object of the third invention isto provide a polishing pad in which a groove is scarcely clogged withabrasive grains or polishing swarf during polishing and, even whencontinuously used for a long period of time, a polishing rate isscarcely reduced. In addition, another object is to provide a processfor manufacturing a semiconductor device using the polishing pad.

In order to solve the aforementioned problems, the present inventorsintensively continued to study and, as a result, found out that theaforementioned objects can be attained by the following polishing pad,which resulted in completion of the invention.

That is, the first invention relates to a polishing pad comprising apolishing layer consisting of a polyurethane resin foam having fine cellstructure, wherein the polyurethane resin foam has a tensile breakingextension of 25 to 120%.

The present inventors found out that, by adjusting a tensile breakingextension of a polyurethane resin foam which is a material for forming apolishing layer at 25 to 120%, both of reduction in a scratch andimprovement in planarization property can be realized.

When a tensile breaking extension of a polyurethane resin foam is lessthan 25%, it becomes easy to cause a scratch on a wafer surface. Inaddition, surface abrasion of a polishing layer becomes greater thannecessary, leading to shortening of a life of polishing pad, and fuzzingon a polishing layer surface after dressing is immediately removed atwafer polishing, and a polishing rate is reduced. On the other hand,when the extension exceeds 120%, planarization property is deteriorated.In addition, “toughness” of a polyurethane resin becomes great, and adressing swarf at dressing becomes great. As a result, a fine pore or agroove on a polishing pad surface is clogged with dressing swarf, and apolishing rate is reduced. The tensile breaking extension is preferably40 to 100%, more preferably 50 to 90%.

The polyurethane resin foam is a reaction cured body of one or two ormore kinds of isocyanate-terminal prepolymers containing ahigh-molecular-weight polyol component and an isocyanate component, anda chain extender, and it is preferable that a NCO wt % (in the case oftwo or more blends, average NCO wt %) of the isocyanate-terminalprepolymer is 9.3 to 15 wt %. A polyurethane resin foam obtained by aprepolymer method is excellent in polishing property, being preferable.

There is a tendency that as a NCO wt % is increased, a tensile breakingextension is reduced and, as a NCO wt % is reduced, a tensile breakingextension is increased. By adjusting a NCO wt % in a specified range, atensile breaking extension of a polyurethane resin foam can be easilyadjusted in the range, as described above. It is preferable that a NCOwt % of the isocyanate-terminal prepolymer is 10 to 11 wt %.

In the first invention, the high-molecular-weight polyol component is ahigh-molecular-weight polyol A having a number average molecular weightof 500 to 850 and a high-molecular-weight polyol B having a numberaverage molecular weight of 900 to 1500, and it is preferable that itscontent ratio is A/B=36/64 to 99/1 (wt %). When a content ratio of ahigh-molecular-weight polyol A is less than 36 wt %, there is a tendencythat planarization property is deteriorated. In addition, “toughness” ofa polyurethane resin becomes great, and a dressing swarf at dressingbecomes great. As a result, a fine pore or a groove on a polishing padsurface is clogged with dressing swarf, and a polishing rate is reduced.On the other hand, when the ratio exceeds 99 wt %, there is a tendencythat a scratch is generated on a wafer surface. In addition, surfaceabrasion of a polishing layer becomes greater than necessary, a life ofa polishing pad is shortened, and fuzzing on a polishing layer surfaceat dressing is immediately removed at wafer polishing, resulting in areduced polishing rate.

A specific gravity of a polyurethane resin foam is preferably in therange of from 0.7 to 0.85 and more preferably in the range of from 0.75to 0.85. If a specific gravity is less than 0.7, various tendenciesarise that a hardness of all of the polishing layer is decreased tothereby deteriorate a planarization characteristic, a life of apolishing pad is shortened because of a larger surface wear of apolishing layer than necessary and a polishing rate is rendered smallerbecause of immediate removal of fluffiness on the surface of a polishingpad after dressing during polishing. On the other hand, when a specificgravity exceeds 0.85, a dressing swarf at dressing becomes great, agroove or a fine pore is clogged with dressing swarf, resulting inclogging, and there is a tendency that a polishing rate is reduced.

In addition, a polyurethane resin foam has an Askar D hardness ofpreferably 56 to 70 degree, more preferably 56 to 65 degree. When anAskar D hardness is less than 56 degree, there is a tendency thatplanarity of a polishing object is reduced. On the other hand, when thehardness is greater than 70 degree, planarity is better, but there is atendency that in-plane uniformity of a polishing object is reduced. Inaddition, it becomes easy to cause a scratch on a surface of a polishingobject.

In addition, it is preferable that a polyurethane resin foam has atensile strength of 15 to 25 MPa. When a tensile strength is less than15 MPa, there is a tendency that planarization property is deterioratedand, the other hand, when the strength exceeds 25 MPa, it becomes easyto cause a scratch on a surface of a polishing object.

In the first invention, a chain extender is preferably aromatic diamine,particularly preferably, 3,5-bis(methylthio)-2,4-toluenediamine and/or3,5-bis(methylthio)-2,6-toluenediamine. By using aromatic diamine and achain extender, reactivity can be sufficiently maintained even at a lowspecific gravity and, since a modulus of a polishing layer can beincreased, planarity and in-plane uniformity of a polishing object areimproved. 3,5-bis(methylthio)-2,4-toluenediamine and3,5-bis(methylthio)-2,6-toluenediamine are aromatic diamine having nochlorine, and they are preferable material from a viewpoint ofenvironmental aspect at wasting.

It is preferable that the isocyanate-terminal prepolymer furthercontains a low-molecular polyol component. In addition, it is preferablethat an isocyanate component is aromatic diisocyanate and cycloaliphaticdiisocyanate. Further, it is preferable that aromatic diisocyanate istoluene diisocyanate, and cycloaliphatic diisocyanate isdicyclohexylmethane diisocyanate. When the above raw material is used, apolishing pad which not only easily adjusts a tensile breaking extensionof a polyurethane resin foam, but also is excellent in polishingproperty can be obtained.

In addition, in the first invention, the polyurethane resin foamcontains a silicone-based nonionic surfactant having no hydroxyl groupat preferably not less than 0.05% by weight and less than 5% by weight,more preferably 0.5 to 4.5% by weight. When an amount of asilicone-based nonionic surfactant is less than 0.05% by weight, atensile breaking extension is not less than 25%, and there is a tendencythat a polyurethane resin foam having fine cells is not obtained. On theother hand, when the amount is not less than 5% by weight, the number ofpores in a foam is increased too much, and there is a tendency that apolyurethane resin foam having a tensile breaking extension of 120% orlower is hardly obtained.

The second invention relates to a polishing pad having a polishing layercomprising a polyurethane resin foam having fine cells, characterized inthat a high-molecular-weight polyol component which is a raw materialcomponent of the polyurethane resin foam is a hydrophobichigh-molecular-weight polyol having a number average molecular weight of500 to 850, and the polyurethane resin foam contains a silicone-basednonionic surfactant having no hydroxyl group at 10 to 20% by weight.

The polishing pad of the second invention has a high polishing rate, andis excellent in planarization property.

The present inventors found out that, by using a hydrophobichigh-molecular-weight polyol having a number average molecular weight of500 to 850 as a high-molecular-weight polyol component which is a rawmaterial component of a polyurethane resin foam, a molecular weightbetween crosslinkings of polyurethane can be reduced, and a modulus canbe increased without increasing a specific gravity of a polyurethaneresin foam (without reducing the number of foams). In addition, when ahydrophobic high-molecular-weight polyol having a number averagemolecular weight of 500 to 850 is used, since dressing property of apolyurethane resin is enhanced, fuzzing on a polishing layer surfaceafter dressing is immediately removed at wafer polishing, andhydrophobicity of a polyurethane resin is enhanced, resulting indeterioration in compatibility with slurry. As a result, a polishingrate tends to decrease. The present inventors found out that theaforementioned problem of reduction in a polishing rate can be solved byusing of a hydrophobic high-molecular-weight polyol having a numberaverage molecular weight of 500 to 850 and a specified amount of asilicone-based nonionic surfactant. In addition, by using thehydrophobic high-molecular-weight polyol, brittleness of a polyurethaneresin foam is increased, and processability of a polishing layer tendsto be remarkably deteriorated, but it was found out that a problem ofprocessability can be solved by blending a specified amount of asilicone-based nonionic surfactant.

When a number average molecular weight of the hydrophobic ofhigh-molecular-weight polyol is less than 500, brittleness of apolyurethane resin foam becomes too high, chipping or cracking occurs ina polishing layer, surface abrasion of a polishing layer becomes greaterthan necessary, a life of a polishing pad is shortened, fuzzing on apolishing layer surface after dressing is immediately removed at waferpolishing, and a polishing rate is reduced. On the other hand, when anumber average molecular weight exceeds 850, it becomes difficult toincrease a modulus of a polishing layer (increase in hardness), andplanarization property cannot be improved.

A number average molecular weight of the hydrophobichigh-molecular-weight polyol is preferably 550 to 800, more preferably600 to 700.

In addition, it is necessary that the polyurethane resin foam contains asilicone-based nonionic surfactant having no hydroxyl group at 10 to 20%by weight, preferably 11 to 15% by weight. When a content of asilicone-based nonionic surfactant is less than 10% by weight,brittleness of a polyurethane resin foam becomes too high, chipping orcracking occurs in a polishing layer, and processability is remarkablydeteriorated. In addition, since dressing property of a polyurethaneresin is enhanced, hydrophobicity of a polyurethane resin becomes toostrong, and compatibility with slurry is deteriorated, a polishing ratetends to decrease. On the other hand, when the content exceeds 20% byweight, it becomes difficult to increase a modulus of a polishing layer(increase in a hardness) due to excessive increase in the number ofpores in a foam, and planarization property cannot be improved.

It is preferable that the polyurethane resin foam is a reaction curedbody of an isocyanate-terminal prepolymer containing the hydrophobichigh-molecular-weight polyol and an isocyanate component, and a chainextender. A polyurethane resin foam obtained by a prepolymer method isexcellent in polishing property, being preferable.

In the second invention, it is preferable that the hydrophobichigh-molecular-weight polyol is a polyester polyol in order to enhancean aggregating force of a polyurethane resin, and maintain highrigidity. In addition, it is also a preferable aspect that a hydrophobichigh-molecular-weight polyol is polytetramethylene glycol.

In addition, it is preferable that the isocyanate component is aromaticdiisocyanate and cycloaliphatic diisocyanate. It is further preferablethat aromatic diisocyanate is toluene diisocyanate, and cycloaliphaticdiisocyanate is dicyclohexylmethane diisocyanate. When theaforementioned raw materials are used, a polishing pad which not onlyeasily adjusts physical property of a polyurethane resin foam, but alsois excellent in polishing property can be obtained.

In addition, in the second invention, it is preferable that a chainextender is aromatic diamine. By using aromatic diamine as a chainextender, it becomes easy to adjust a curing time, a specific gravityand a hardness of a polishing layer etc. In addition, it is preferablethat the aromatic diamine is non-halogen-based aromatic diamine in viewof an environmental aspect.

The polyurethane resin foam has a specific gravity of preferably 0.65 to0.86, more preferably 0.7 to 0.8. When a specific gravity is less than0.65, there is a tendency that a surface hardness of a polishing layeris reduced, planarity of a polishing object (wafer) is reduced, and lifeproperty is deteriorated. On the other hand, when a specific gravityexceeds 0.86, there is a tendency that the number of pores per unit areais decreased, and a polishing rate is reduced.

It is preferable that the polyurethane resin foam has an Askar Dhardness of 50 to 65 degree. When an Askar D hardness is less than 50degree, planarity of a polishing object is reduced and, when thehardness is greater than 65 degree, planarity is better, but in-planeuniformity of a polishing subject tends to decrease.

It is preferable that the polyurethane resin foam has a tensile strengthof 15 to 25 MPa. When a tensile strength is less than 15 MPa,planarization property of a polishing pad tends to decrease and, on theother hand, the strength exceeds 25 MPa, it becomes easy to cause ascratch on a polishing object (wafer).

It is preferable that the polyurethane resin foam has a tensile breakingextension of 25 to 100%. When a tensile breaking extension is less than25%, there is a tendency that surface abrasion becomes greater thannecessary, a life of a polishing pad is shortened, fuzzing on apolishing layer surface after dressing is immediately removed at waferpolishing, and a polishing rate is reduced. On the other hand, when theextension exceeds 100%, planarity of a polishing object tends todecrease.

Also, the second invention relates to a process for manufacturing apolishing pad comprising a step (1) of mixing a first componentcomprising an isocyanate-terminal prepolymer and a second componentcomprising a chain extender, and curing the mixture to prepare apolyurethane resin foam,

wherein the step (1) is a step of adding a silicone-based nonionicsurfactant having no hydroxyl group to a first component comprising anisocyanate-terminal prepolymer so that a content of the surfactantbecomes 10 to 20% by weight, stirring the first component with anon-reactive gas to prepare a bubble dispersion liquid in which thenon-reactive gas is dispersed as a fine bubble, mixing a secondcomponent comprising a chain extender into the bubble dispersion liquid,and curing the mixture to prepare a polyurethane resin foam, and ahigh-molecular-weight polyol component which is a raw material componentof the isocyanate-terminal prepolymer is a hydrophobichigh-molecular-weight polyol having a number average molecular weight of500 to 850, and a polishing pad manufactured by the process.

The third invention relates to a polishing pad which comprises apolyurethane resin foam having fine cells and contains a polishing layerhaving a depression and protrusion structure on a polishing surface,characterized in that the polyurethane resin foam has an Ascar Dhardness of 45 to 55 degree, a specific gravity of 0.8 to 0.86, and atensile breaking extension of 120 to 150%.

In the case where the previous polishing pad with a groove is used, asthe reason why a polishing rate is gradually reduced as polishingprocessing is performed, the following reason is considered. On asurface of the polishing pad with a groove, a groove or a fine pore isprovided in order to retain or renew a polishing slurry, and removegenerated polishing swarf. However, in the previous polishing pad, agroove or a fine pore is easily clogged with abrasive grains orpolishing swarf in a polishing slurry. For this reason, it is necessaryto frequently grind a polishing pad surface with dressing to renew intoa new surface. The reason why the previous polishing pad is clogged isthat 1) a specific gravity of a polishing layer is high, and 2) amaterial itself of a polishing layer has “toughness”. Particularly, whena material itself of a polishing layer has “toughness”, it is consideredthat a polishing swarf of a polishing layer generated at polishingbecomes great, the polishing swarf is clogged into a groove or a finepore, easily causing clogging. When a specific gravity of a polishinglayer is simply reduced, planarization property is deteriorated, surfaceabrasion of a polishing layer becomes greater than necessary, a life ofpolishing pad is shortened, fuzzing on a polishing layer surface afterdressing is immediately removed at wafer polishing, and a polishing rateis reduced, being not preferable.

The present inventors found out that, by adjusting an Askar D hardnessof a polyurethane resin foam which is a material for forming a polishinglayer at 45 to 55 degree, a specific gravity of the foam at 0.8 to 0.86,and a tensile breaking extension of the foam at 120 to 150%, a hardnesscan be reduced without reducing a specific gravity of a polishing layer,and “toughness” of a polyurethane resin is suitably reduced to make apolishing swarf small, thereby, clogging can be suppressed.

When an Askar D hardness of a polyurethane resin foam is less than 45degree, planarity of a polishing object is reduced. On the other hand,when the hardness is greater than 55 degree, planarity is better, butin-plane uniformity of a polishing object tends to decrease. It ispreferable that an Askar D hardness of the polyurethane resin foam is 49to 54 degree.

In addition, when a specific gravity of a polyurethane resin foam isless than 0.8, planarization property is deteriorated, surface abrasionof a polishing layer becomes greater than necessary, a life of apolishing pad is shortened, fuzzing on a polishing layer surface afterdressing is immediately removed at wafer polishing, and a polishing rateis reduced. On the other hand, when a specific gravity exceeds 0.86, adressing swarf at dressing becomes great, the dressing swarf is cloggedinto a groove or a fine pore, causing clogging, and a polishing rate isreduced. It is preferable that a specific gravity of the polyurethaneresin foam is 0.8 to 0.83.

In addition, when a tensile breaking extension of a polyurethane resinfoam is less than 120%, surface abrasion of a polishing layer becomesgreater than necessary, a life of a polishing pad is shortened, fuzzingon a polishing layer surface after dressing is immediately removed atwafer polishing, and a polishing rate is reduced. On the other hand,when the extension exceeds 150%, since “toughness” of a polyurethaneresin itself becomes too great, a dressing swarf at dressing becomesgreat. As a result, a dressing swarf is clogged into a groove or a finepore, causing clogging, and a polishing rate is reduced. It ispreferable that a tensile breaking extension of the polyurethane resinfoam is 125 to 145%.

It is preferable that the polyurethane resin foam is a reaction curedbody of one or two or more kinds of isocyanate-terminal prepolymerscontaining a high-molecular-weight polyol component and an isocyanatecomponent, and a chain extender, and a NCO wt % (in the case of two ormore blends, average NCO wt %) is 9.3 to 10.5% by weight. A polyurethaneresin foam obtained by a prepolymer method is excellent in polishingproperty, being preferable.

There is a tendency that as a NCO wt % becomes greater, a tensilebreaking extension is reduced and, as a NCO wt % is reduced, a tensilebreaking extension becomes greater. As described above, by adjusting aNCO wt % in a specified range, a tensile breaking extension of apolyurethane resin foam can be easily adjusted in the range. It ispreferable that a NCO wt % of the isocyanate-terminal prepolymer is 9.4to 10% by weight.

In the third invention, it is preferable that the high-molecular-weightpolyol component is a high-molecular-weight polyol A having a numberaverage molecular weight of 500 to 850, and a high-molecular-weightpolyol B having a number average molecular weight of 900 to 1500, andits content ratio is A/B=5/95 to 35/65 (wt %). When a content ratio of ahigh-molecular-weight polyol A is less than 5% by weight, since“toughness” of a polyurethane resin itself becomes too great, a dressingswarf at dressing becomes great. As a result, a dressing swarf isclogged into a groove or a fine pore, causing clogging, and a polishingrate becomes unstable. On the other hand, when the ratio exceeds 35% byweight, brittleness of a polyurethane resin is increased, and lifeproperty of a polishing pad is deteriorated. In addition, a scratch iseasily generated.

In addition, it is preferable that a polyurethane resin foam has atensile strength of 15 to 25 MPa. When a tensile strength is less than15 MPa, planarization property is deteriorated and, on the other hand,when a tensile strength exceeds 25 MPa, a scratch tends to be generated.

In the third invention, a chain extender is preferably aromatic diamine,particularly preferably 3,5-bis(methylthio)-2,4-toluenediamine and/or3,5-bis(methylthio)-2,6-toluenediamine. Since reactivity can besufficiently maintained, and a modulus of a polishing layer can befurther increased by using aromatic diamine as a chain extender,planarity and in-plane uniformity of a polishing object are improved.3,5-bis(methylthio)-2,4-toluenediamine and3,5-bis(methylthio)-2,6-toluenediamine are aromatic diamine containingno chlorine, and they are a particularly preferable material from aviewpoint of an environmental aspect at wasting.

It is preferable that the isocyanate-terminal prepolymer furthercontains a low-molecular polyol component. In addition, it is preferablethat an isocyanate component is aromatic diisocyanate and cycloaliphaticdiisocyanate. It is further preferable that aromatic diisocyanate istoluene diisocyanate, and cycloaliphatic diisocyanate is dicyclohexylmethane diisocyanate. When the aforementioned raw materials are used, apolishing pad which not only easily adjusts a hardness, a specificgravity and a tensile breaking extension of a polyurethane resin foam,but also is excellent in polishing property can be obtained.

In addition, in the third invention, the polyurethane resin foamcontains a silicone-based nonionic surfactant having no hydroxyl groupat preferably 0.05 to 10% by weight, more preferably 0.5 to 10% byweight. When an amount of a silicone-based nonionic surfactant is lessthan 0.05% by weight, there is a tendency that a foam of fine pores isnot obtained. On the other hand, when the amount exceeds 10% by weight,there is a tendency that the number of pores in a foam is increased toomuch, and an objective polyurethane resin foam is hardly obtained.

In addition, a dressing speed of the polishing pad of the thirdinvention is preferably 5 to 10 μm/min, more preferably 6 to 8 μm/min.When a dressing speed is less than 5 μm/min, a dressing swarf atdressing becomes great, a dressing swarf is clogged into a groove or afine pore, causing clogging, and a polishing rate tends to decrease. Onthe other hand, when a dressing speed exceeds 10 μm/min, there is atendency that surface abrasion of a polishing layer becomes greater thannecessary, a life of a polishing pad is shortened, fuzzing on apolishing layer surface after dressing is immediately removed at waferpolishing, and a polishing rate is reduced.

Also, the invention relates to a process for manufacturing asemiconductor device, comprising a step of polishing a surface of asemiconductor wafer using the aforementioned polishing pad.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an example of construction of apolishing apparatus used in CMP.

DETAILED DESCRIPTION OF THE INVENTION

The polishing pad of the first to third inventions has a polishing layerconsisting of a polyurethane resin foam having fine cell structure. Thepolishing pad of the invention may contain only the polishing layer, ormay be a laminate of a polishing layer and other layer (e.g. cushionlayer etc.).

Since a polyurethane resin is excellent in abrasion resistance, and apolymer having desired physical property can be easily obtained byvarious changing a low material composition, the resin is a particularlypreferable as a material for forming a polishing layer.

The polyurethane resin is constituted of an isocyanate component, apolyol component (a high-molecular-weight polyol component and alow-molecular-weight polyol component) and a chain extender.

As the isocyanate component, a compound known in the field ofpolyurethane can be used without particular limitation. The isocyanatecomponent includes, for example, aromatic diisocyanates such as2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenyl methane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylenediisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate andm-xylylene diisocyanate, aliphatic diisocyanates such as ethylenediisocyanate, 2,2,4-trimethyl hexamethylene diisocyanate and1,6-hexamethylene diisocyanate, and cycloaliphatic diisocyanates such as1,4-cyclohexane diisocyanate, 4,4′-dicyclohexyl methane diisocyanate,isophorone diisocyanate and norbornane diisocyanate. These may be usedalone or as a mixture of two or more thereof.

As the isocyanate component, it is possible to use not only theabove-described diisocyanate compounds but also multifunctional(trifunctional or more) polyisocyanates. As the multifunctionalisocyanate compounds, a series of diisocyanate adduct compounds arecommercially available as Desmodul-N (Bayer) and Duranate™ (AsahiChemical Industry Co., Ltd.).

Among the aforementioned isocyanate components, it is preferable to usearomatic diisocyanate and cycloaliphatic diisocyanate jointly, and it isparticularly preferable to use toluene diisocyanate anddicyclohexylmethane diisocyanate jointly.

As the high-molecular-weight polyol, a compound known in the field ofpolyurethane can be used without particular limitation. Thehigh-molecular-weight polyol includes, for example, polyether polyolsrepresented by polytetramethylene ether glycol and polyethylene glycol,polyester polyols represented by polybutylene adipate, polyesterpolycarbonate polyols exemplified by reaction products of polyesterglycols such as polycaprolactone polyol and polycaprolactone withalkylene carbonate, polyester polycarbonate polyols obtained by reactingethylene carbonate with a multivalent alcohol and reacting the resultingreaction mixture with an organic dicarboxylic acid, and polycarbonatepolyols obtained by ester exchange reaction of a polyhydroxyl compoundwith aryl carbonate. These may be used singly or as a mixture of two ormore thereof.

No limitation is imposed on a number-average molecular weight of ahigh-molecular-weight polyol but it is preferably in the range of from500 to 2000 from the viewpoint of an elastic characteristic of anobtained polyurethane resin. If a number-average molecular weightthereof is less than 500, a polyurethane resin obtained by using thepolyol does not have a sufficient elastic characteristic and easy to befragile, and a polishing pad made from the polyurethane resin isexcessively hard, which sometimes causes scratches to be generated on asurface of an object to be polished. Moreover, since a polishing pad iseasy to be worn away, it is unpreferable from the viewpoint of a life ofa polishing pad. On the other hand, if a number-average molecular weightthereof exceeds 2000, a polishing pad made from a polyurethane resinobtained from such a polyol is unpreferably soft to thereby disable asufficiently satisfiable planarity to be earned.

In this regard, in the second invention, as a high-molecular-weightpolyol component, a hydrophobic high-molecular-weight polyol having anumber average molecular weight of 500 to 850 is used.

The hydrophobic high-molecular-weight polyol has no hydrophilic groupother than a hydroxyl group which reacts with an isocyanate group.

A hydrophilic group other than a hydroxyl group is generally afunctional group or a salt containing an element such as oxygen,nitrogen and sulfur and, examples include functional groups such as—NH₂, —CONH₂, —NHCONH₂, —SH, —SO₃H, —OSO₃H, —(CH₂CH₂O)n-, and —COOH, andsalts such as —SO₃M (M:alkali metal), —OSO₃M, —COOM, and —NR₃X (R:alkylgroup, X:halogen).

Examples of the hydrophobic high-molecular-weight polyol include ahydroxyl-terminal polyester polyol, a polycarbonate polyol, a polyesterpolycarbonate polyol, a polyether polyol, a polyether polycarbonatepolyol, a polyester amide, a phenol resin polyol, an epoxy polyol, apolybutadiene polyol, and a polyisoprene polyol.

Examples of the polyester polyol include polypropylene adipate,polybutylene adipate, polyhexamethylene adipate, and polycaprolactonepolyol.

Examples of the polyether polyol include polyhexamethylene glycol(PHMG), polytetramethylene glycol (PTMG), and polypropylene glycol(PPG).

Examples of the polyether polycarbonate polyol include reaction productsof a diol such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol,polypropylene glycol and/or polytetramethylene glycol with phosgene,diallyl carbonate (e.g. diphenyl carbonate) or cyclic carbonate (e.g.propylene carbonate).

Examples of the polyester polycarbonate polyol include reaction productsof polyester glycol such as polycaprolactone polyol etc. with alkylenecarbonate, and products obtained by reacting ethylene carbonate and apolyhydric alcohol, and reacting the resulting reaction mixture withorganic dicarboxylic acid.

The aforementioned hydrophobic high-molecular-weight polyols may be onekind of the polyols, or two or more kinds may be used jointly.

In the second invention, it is preferable that the hydrophobichigh-molecular-weight polyol is polyester polyol. In addition, it isalso a preferable aspect that the hydrophobic high-molecular-weightpolyol is polytetramethylene glycol.

In the first invention, it is preferable to use a high-molecular-weightpolyol A having a number average molecular weight of 500 to 850 and ahigh-molecular-weight polyol B having a number average molecular weightof 900 to 1500 jointly. It is further preferable that bothhigh-molecular-weight polyols are hydrophobic. By using bothhigh-molecular-weight polyols jointly, a tensile breaking extension of apolyurethane resin foam can be adjusted in a range of 25 to 120%. Aratio of blending a high-molecular-weight polyol A and ahigh-molecular-weight polyol B is preferably A/B=36/64 to 99/1 (wt %),more preferably A/B=38/62 to 80/20 (wt %), further preferably A/B=40/60to 70/30 (wt %).

In the third invention, it is preferable to use a high-molecular-weightpolyol A having a number average molecular weight of 500 to 850 and ahigh-molecular-weight polyol B having a number average molecular weightof 900 to 1500 jointly. It is further preferable that bothhigh-molecular-weight polyols are hydrophobic. By using bothhigh-molecular-weight polyols jointly, it becomes easy to adjust ahardness, a specific gravity and a tensile breaking extension of apolyurethane resin foam in objective ranges. A ratio of blending ahigh-molecular-weight polyol A and a high-molecular-weight polyol B ispreferably A/B=5/95 to 35/65 (wt %), more preferably A/B=10/90 to 30/70(wt %), particularly preferably A/B=20/80 to 30/70 (wt %).

Examples of the low-molecular-weight polyol that can be used togetherwith a high-molecular-weight polyol described above include: ethyleneglycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol,1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,6-hexanediol,neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol,diethylene glycol, triethyleneglycol, 1,4-bis(2-hydroxyethoxy)benzene,trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol,tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol,dulcitol, sucrose, 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol,diethanolamine, N-methyldiethanolamine, triethanolamine and the like.Other examples that can be used together with the high-molecular-weightpolyol also include: low-molecular-weight polyamine such asethylenediamine, tolylenediamine, diphenylmethanediamine,diethylenetriamine and the like. Still other examples that can be usedtogether with the high-molecular-weight polyol also include:alcoholamines such as monoethanolamine, 2-(2-aminoethylamino)ethanol,monopropanolamine and the like. The low-molecular-weight polyols and thelow-molecular-weight polyamines may be used either alone or incombination of two or more kinds. A mixing quantity of each of alow-molecular-weight polyol and a low-molecular-weight polyamine is notspecifically limited and properly determined so as to matchcharacteristics required for a manufactured polishing pad (a polishinglayer). A molecular weight of the low-molecular-weight polyol or thelow-molecular-weight polyamine is less than 500, preferably not morethan 250.

In the case where a polyurethane resin foam is produced by means of aprepolymer method, a chain extender is used in curing of a prepolymer. Achain extender is an organic compound having at least two activehydrogen groups and examples of the active hydrogen group include: ahydroxyl group, a primary or secondary amino group, a thiol group (SH)and the like. Concrete examples of the chain extender include:polyamines such as 4,4′-methylenebis(o-chloroaniline) (MOCA),2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis(2,3-dichloroaniline),3,5-bis(methylthio)-2,4-toluenediamine,3,5-bis(methylthio)-2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine,3,5-diethyltoluene-2,6-diamine, trimethylene glycol-di-p-aminobenzoate,polytetramethylene oxide-di-p-aminobenzoate,4,4′-diamino-3,3′,5,5′-tetraethyldiphenylmethane,4,4′-diamino-3,3′-diisopropyl-5.5′-dimethyldiphenylmethane,4,4′-diamino-3,3′,5,5′-tetraisopropyldiphenylmethane,1,2-bis(2-aminophenylthio)ethane,4,4′-diamino-3,3′-diethyl-5.5′-dimethyldiphenylmethane,N,N′-di-sec-butyl-4,4′-diaminophenylmethane,3,3′-diethyl-4,4′-diaminodiphenylmethane, m-xylylenediamine,N,N′-di-sec-butyl-p-phenylenediamine, m-phenylenediamine andp-xylylenediamine; low-molecular-weight polyol component; and alow-molecular-weight polyamine component. The chain extenders describedabove may be used either alone or in mixture of two kinds or more.Especially preferably used are halogen free aromatic diamines such as3,5-bis(methylthio)-2,4-toluenediamine and3,5-bis(methylthio)-2,6-toluenediamine.

A ratio between an isocyanate component, a polyol component and a chainextender in the invention can be altered in various ways according tomolecular weights thereof, desired physical properties of a polishingpad and the like. In order to obtain a polishing pad with desiredpolishing characteristics, a ratio of the number of isocyanate groups inan isocyanate component relative to a total number of active hydrogengroups (hydroxyl groups+amino groups) in a polyol component and a chainextender is preferably in the range of from 0.80 to 1.20 and morepreferably in the range of from 0.99 to 1.15. When the number ofisocyanate groups is outside the aforementioned range, there is atendency that curing deficiency is caused, required tensile breakingextension, specific gravity and hardness are not obtained, and polishingproperty is deteriorated.

A polyurethane resin foam can be produced by applying a melting method,a solution method or a known polymerization technique, among whichpreferable is a melting method, consideration being given to a cost, aworking environment and the like.

Manufacture of a polyurethane resin foam is enabled by means of either aprepolymer method or a one shot method, of which preferable is aprepolymer method in which an isocyanate-terminated prepolymer issynthesized from an isocyanate component and a polyol component inadvance, with which a chain extender is reacted since physicalproperties of an obtained polyurethane resin is excellent.

Note that an isocyanate-terminated prepolymer with a molecular weight ofthe order in the range of from 800 to 5000 is preferable because ofexcellency in workability and physical properties.

Manufacture of the polyurethane resin foam is to mix the first componentcontaining an isocyanate group containing compound and the secondcomponent containing an active hydrogen group containing compound tothereby cure the reaction product. In the prepolymer method, anisocyanate-terminated prepolymer serves as an isocyanate groupcontaining compound and a chain extender serves as an active hydrogengroup containing compound. In the one shot method, an isocyanatecomponent serves as an isocyanate group containing compound, and a chainextender and a polyol component combined serves as an active hydrogencontaining compound.

Manufacturing methods of a polyurethane resin foam include: a method inwhich hollow beads are added, a mechanically foaming method, achemically foaming method and the like.

Particularly, a mechanically foaming method using a silicone-basedsurfactant having no active hydrogen group which is a copolymer ofpolyalkylsiloxane and polyether is preferable. As such thesilicone-based nonionic surfactant, L5340 (manufactured by NihonunicaCorporation) etc. are exemplified as a suitable compound.

Various additives may be mixed; such as a stabilizer including anantioxidant, a lubricant, a pigment, a filler, an antistatic agent andothers.

Description will be given of an example of a method of producing apolyurethane resin foam of a fine cell type constituting a polishing pad(a polishing layer) below. A method of manufacturing such a polyurethaneresin foam has the following steps:

1) a foaming step of preparing a bubble dispersion liquid of anisocyanate-terminated prepolymer (first component), wherein a silicone-based nonionic surfactant is added into anisocyanate-terminated prepolymer, which is agitated in the presence of anon-reactive gas to thereby disperse the non-reactive gas into theprepolymer as fine bubbles and obtain a bubble dispersion liquid. In acase where the prepolymer is solid at an ordinary temperature, theprepolymer is preheated to a proper temperature and used in a moltenstate.2) a curing agent (chain extender) mixing step, wherein a chain extender (second component) is added into the bubbledispersion liquid, which is agitated to thereby obtain a foamingreaction liquid.3) a casting step, wherein the forming reaction liquid is cast into a mold.4) a curing step, wherein the foaming reaction liquid having been cast into the mold isheated and reaction-cured.

The non-reactive gas used for forming fine bubbles is preferably notcombustible, and is specifically nitrogen, oxygen, a carbon dioxide gas,a rare gas such as helium and argon, and a mixed gas thereof, and theair dried to remove water is most preferable in respect of cost.

As a stirrer for dispersing the silicone-based nonionicsurfactant-containing first component to form fine bubbles with thenon-reactive gas, known stirrers can be used without particularlimitation, and examples thereof include a homogenizer, a dissolver, atwin-screw planetary mixer etc. The shape of a stirring blade of thestirrer is not particularly limited either, but a whipper-type stirringblade is preferably used to form fine bubbles.

In a preferable mode, different stirrers are used in stirring forforming a bubble dispersion liquid in the stirring step and in stirringfor mixing an added chain extender in the mixing step, respectively. Inparticular, stirring in the mixing step may not be stirring for formingbubbles, and a stirrer not generating large bubbles is preferably used.Such a stirrer is preferably a planetary mixer. The same stirrer may beused in the stirring step and the mixing step, and stirring conditionssuch as revolution rate of the stirring blade are preferably regulatedas necessary.

In the method of producing the polyurethane foam with fine cells,heating and post-curing of the foam obtained after casting and reactingthe forming reaction liquid in a mold until the dispersion lost fluidityare effective in improving the physical properties of the foam, and areextremely preferable. The forming reaction liquid may be cast in a moldand immediately post-cured in a heating oven, and even under suchconditions, heat is not immediately conducted to the reactivecomponents, and thus the diameters of cells are not increased. Thecuring reaction is conducted preferably at normal pressures to stabilizethe shape of cells.

In the production of the polyurethane foam, a known catalyst promotingpolyurethane reaction, such as tertiary amine-based catalysts, may beused. The type and amount of the catalyst added are determined inconsideration of flow time in casting in a predetermined mold after themixing step.

Production of the polyurethane foam may be in a batch system where eachcomponent is weighed out, introduced into a vessel and mixed or in acontinuous production system where each component and a non-reactive gasare continuously supplied to, and stirred in, a stirring apparatus andthe resulting forming reaction liquid is transferred to produce moldedarticles.

A manufacturing method of a polishing pad may be performed in ways: inone of which a prepolymer which is a raw material from which a polishingpad (a polishing layer) is made is put into a reactor, thereafter achain extender is mixed into the prepolymer, the mixture is agitated,thereafter the mixture is cast into a mold with a predetermined size tothereby prepare a block and the block is sliced with a slicer like aplaner or a band saw; and in another of which in the step of castinginto the mold, a thin sheet may be directly produced. Besides, a stillanother way may be adopted in which a resin of raw material is melted,the melt is extruded through a T die to thereby mold a polyurethaneresin foam directly in the shape of a sheet.

An average cell diameter of a polyurethane resin foam is preferably inthe range of from 30 to 80 μm and more preferably in the range of from30 to 60 μm. If an average cell diameter falls outside the range, atendency arises that a polishing rate is decreased and a planarity of anobject to be polished (a wafer) after polishing is reduced.

A polishing pad (polishing layer) of the invention is preferablyprovided with a depression and a protrusion structure for holding andrenewing a slurry. Though in a case where the polishing layer is formedwith a fine foam, many openings are on a polishing surface thereof whichworks so as to hold the slurry, a depression and protrusion structureare preferably provided on the surface of the polishing side thereof inorder to achieve more of holdability and renewal of the slurry or inorder to prevent induction of dechuck error, breakage of a wafer ordecrease in polishing efficiency. The shape of the depression andprotrusion structure is not particularly limited insofar as slurry canbe retained and renewed, and examples include latticed grooves,concentric circle-shaped grooves, through-holes, non-through-holes,polygonal prism, cylinder, spiral grooves, eccentric grooves, radialgrooves, and a combination of these grooves. The groove pitch, groovewidth, groove thickness etc. are not particularly limited either, andare suitably determined to form grooves. These depression and protrusionstructure are generally those having regularity, but the groove pitch,groove width, groove depth etc. can also be changed at each certainregion to make retention and renewal of slurry desirable.

The method of forming the depression and protrusion structure is notparticularly limited, and for example, formation by mechanical cuttingwith a jig such as a bite of predetermined size, formation by castingand curing resin in a mold having a specific surface shape, formation bypressing resin with a pressing plate having a specific surface shape,formation by photolithography, formation by a printing means, andformation by a laser light using a CO₂ gas laser or the like.

No specific limitation is placed on a thickness of a polishing layer,but a thickness thereof is about 0.8 to 4 mm, preferably 1.0 to 2.5 mm.The method of preparing the polishing layer of this thickness includes amethod wherein a block of the fine-cell foam is cut in predeterminedthickness by a slicer in a bandsaw system or a planing system, a methodthat involves casting resin into a mold having a cavity of predeterminedthickness and curing the resin, a method of using coating techniques andsheet molding techniques, etc.

The range of the thickness of the polishing layer is preferably 100 μmor less. When the range of the thickness is higher than 100 μm, largeundulation is caused to generate portions different in a contactingstate with an object of polishing, thus adversely influencing polishingcharacteristics. To solve the range of the thickness of the polishinglayer, the surface of the polishing layer is dressed generally in aninitial stage of polishing by a dresser having abrasive grains ofdiamond deposited or fused thereon, but the polishing layer outside ofthe range described above requires a longer dressing time to reduce theefficiency of production.

As a method of suppressing the range of thickness, there is also amethod of buffing the surface of the polishing layer having apredetermined thickness. Buffing is conducted preferably stepwise byusing polishing sheets different in grain size.

A polishing pad of the invention may also be a laminate of a polishinglayer and a cushion sheet adhered to each other.

The cushion sheet (cushion layer) compensates for characteristics of thepolishing layer. The cushion layer is required for satisfying bothplanarity and uniformity which are in a tradeoff relationship in CMP.Planarity refers to flatness of a pattern region upon polishing anobject of polishing having fine unevenness generated upon patternformation, and uniformity refers to the uniformity of the whole of anobject of polishing. Planarity is improved by the characteristics of thepolishing layer, while uniformity is improved by the characteristics ofthe cushion layer. The cushion layer used in the polishing pad of thepresent invention is preferably softer than the polishing layer.

The material forming the cushion layer is not particularly limited, andexamples of such material include a nonwoven fabric such as a polyesternonwoven fabric, a nylon nonwoven fabric or an acrylic nonwoven fabric,a nonwoven fabric impregnated with resin such as a polyester nonwovenfabric impregnated with polyurethane, polymer resin foam such aspolyurethane foam and polyethylene foam, rubber resin such as butadienerubber and isoprene rubber, and photosensitive resin.

Means for adhering the polishing layer to the cushion layer include: forexample, a method in which a double sided tape is sandwiched between thepolishing layer and the cushion layer, followed by pressing.

The double sided tape is of a common construction in which adhesivelayers are provided on both surfaces of a substrate such as a nonwovenfabric or a film. It is preferable to use a film as a substrate withconsideration given to prevention of permeation of a slurry into acushion sheet. A composition of an adhesive layer is, for example, of arubber-based adhesive, an acrylic-based adhesive or the like. Anacrylic-based adhesive is preferable because of less of a content ofmetal ions, to which consideration is given. Since a polishing layer anda cushion sheet is sometimes different in composition from each other,different compositions are adopted in respective adhesive layers ofdouble sided tape to thereby also enable adhesive forces of therespective adhesive layers to be adjusted to proper values.

A polishing pad of the invention may be provided with a double sidedtape on the surface of the pad adhered to a platen. As the double sidedtape, a tape of a common construction can be used in which adhesivelayers are, as described above, provided on both surfaces of asubstrate. As the substrate, for example, a nonwoven fabric or a film isused. Preferably used is a film as a substrate since separation from theplaten is necessary after the use of a polishing pad. As a compositionof an adhesive layer, for example, a rubber-based adhesive or anacrylic-based adhesive is exemplified. Preferable is an acrylic-basedadhesive because of less of metal ions in content to which considerationis given.

A semiconductor device is fabricated after operation in a step ofpolishing a surface of a semiconductor wafer with a polishing pad. Theterm, a semiconductor wafer, generally means a silicon wafer on which awiring metal and an oxide layer are stacked. No specific limitation isimposed on a polishing method of a semiconductor wafer or a polishingapparatus, and polishing is performed with a polishing apparatusequipped, as shown in FIG. 1, with a polishing platen 2 supporting apolishing pad (a polishing layer) 1, a polishing head 5 holding asemiconductor wafer 4, a backing material for applying a uniformpressure against the wafer and a supply mechanism of a polishing agent3. The polishing pad 1 is mounted on the polishing platen 2 by adheringthe pad to the platen with a double sided tape. The polishing platen 2and the polishing head 5 are disposed so that the polishing pad 1 andthe semiconductor wafer 4 supported or held by them oppositely face eachother and provided with respective rotary shafts 6 and 7. A pressuremechanism for pressing the semiconductor wafer 4 to the polishing pad 1is installed on the polishing head 5 side. During polishing, thesemiconductor wafer 4 is polished by being pressed against the polishingpad 1 while the polishing platen 2 and the polishing head 5 are rotatedand a slurry is fed. No specific limitation is placed on a flow rate ofthe slurry, a polishing load, a polishing platen rotation number and awafer rotation number, which are properly adjusted.

Protrusions on the surface of the semiconductor wafer 4 are therebyremoved and polished flatly. Thereafter, a semiconductor device isproduced therefrom through dicing, bonding, packaging etc. Thesemiconductor device is used in an arithmetic processor, a memory etc.

EXAMPLES

Description will be given of the invention with examples, while theinvention is not limited to description in the examples.

[Measurement and Evaluation Method]

(Measurement of Number-Average Molecular Weight)

A number-average molecular weight was measured by GPC (a Gel PermeationChromatography) and a value as measured was converted in terms ofstandard polystylene molecular weight, and the apparatus and conditionsin operation were as follows:

GPC apparatus was an apparatus manufactured by Shimadzu Corp., withModel Number of LC-10A.Columns that were used in measurement were ones manufactured by PolymerLaboratories Co., in which three columns were in connection including(PL gel, 5 μm and 500 Å), (PL gel, 5 μm and 100 Å) and (PL gel, 5 μm and50 Å).A flow rate was 1.0 ml/min.A concentration was 1.0 g/l.An injection quantity was 40 μl.A column temperature was 40° C.An eluent was tetrahydrofuran.

(Measurement of Tensile Breaking Extension and Tensile Strength)

According to JIS K7312-1996, a prepared polyethylene resin foam waspunched into a shape of dumbbell No. 3 to obtain a sample. The samplewas aged for 24 hours under condition of 22° C. and 66% RH and,thereafter, a tensile test was performed. A tensile breaking extensionand a tensile strength were measured. As a tensile tester, InstronUniversal Testing Machine (Model 4300, manufactured by Instron) was usedand, as a software, a video extension meter controlled by series IX wasused.

(Measurement of Average Cell Diameter)

A manufactured polyurethane resin foam was sliced with a microtomecutter into measurement samples each with the thinnest possiblethickness of 1 mm or less. A surface of a sample was photographed with ascanning electron microscope (manufactured by Hitachi Science System Co.with a model number of S-3500N) at a magnification of ×100. An effectivecircular diameter of each of all cells in an arbitrary area was measuredwith an image analyzing soft (manufactured by MITANI Corp. with a tradename WIN-ROOF) and an average cell diameter was calculated from themeasured values.

(Measurement of Specific Gravity)

Determined according to JIS Z8807-1976. A manufactured polyurethaneresin foam cut out in the form of a strip of 4 cm×8.5 cm (thickness:arbitrary) was used as a sample for measurement of specific gravity andleft for 16 hours in an environment of a temperature of 23±2° C. and ahumidity of 50%±5%. Measurement was conducted by using a specificgravity hydrometer (manufactured by Sartorius Co., Ltd).

(Measurement of Hardness)

Measurement is conducted according to JIS K6253-1997. A manufacturedpolyurethane resin foam cut out in a size of 2 cm×2 cm (thickness:arbitrary) was used as a sample for measurement of hardness and left for16 hours in an environment of a temperature of 23±2° C. and a humidityof 50%±5%. At the time of measurement, samples were stuck on one anotherto a thickness of 6 mm or more. A hardness meter (Asker D hardnessmeter, manufactured by Kobunshi Keiki Co., Ltd.) was used to measurehardness.

(Evaluation of Polishing Characteristics)

Using SPP600S (manufactured by Okamoto Machine Tool Works, Ltd.) as apolishing apparatus, and using a prepared polishing pad, a polishingrate was assessed. A thermally oxidized membrane of 1 μm was made on asilicon wafer of 8 inch, one of the membrane was polished above 0.5 μm,and an initial polishing rate was calculated from a time thereupon. Inaddition, polishing was repeated by the similar method, to performpolishing for an accumulated time of 10 hours, and a polishing rateafter 10 hours was measured. For measuring a thickness of an oxidizedmembrane, an interference film thickness measuring instrument(manufactured by Otsuka Electronics Co., Ltd.) was used. Duringpolishing, silica slurry (SS12 manufactured by Cabot) was added at aflow rate of 150 ml/min. Polishing loading was 350 g/cm², the number ofrevolutions of the polishing platen was 35 rpm, and the number ofrevolutions of the wafer was 30 rpm.

In addition, for assessing planarity, a thermally oxidized membrane wasdeposited 0.5 μm on a 8 inch silicon wafer, patterning of L/S (line andspace)=25 μm/5 μm and L/S=5 μm/25 μm was performed, and an oxidizedmembrane (TEOS) was further deposited 1 μm to prepare a wafer with apattern at an initial step of 0.5 μm. This wafer was polished under theaforementioned polishing condition, and an abrasion amount of a bottompart of a 25 μm space was measured at a global step of 2000 Å orsmaller, thereby, planarity was assessed. As a value of an abrasionamount is smaller, planarity can be said to be excellent.

(Measurement of Dressing Speed)

A surface of a manufactured polishing pad was uniformly dressed with adiamond dresser (manufactured by Asahi Diamond Co. with a trade name ofM Type #100 in the shape of a circle with a diameter of 20 cm) whilebeing rotated. A dresser load at this time was set to 450 g/cm², apolishing platen rotation number was set to 30 rpm, a dresser rotationnumber was set to 15 rpm and a dressing time was set to 100 min. Adressing speed was calculated from thickness values of the polishing padas measured before and after dressing.

(Assessment of Clogging)

Whether there is clogging in a groove on a polishing pad surface afterthe aforementioned polishing for 10 hours or not was visually confirmed,and clogging was assessed based on the following criteria.

◯: A ratio of clogging is less than 10% of all grooves.Δ: A ratio of clogging is not less than 10% and less than 20% of allgrooves.x: A ratio of clogging is not less than 20% of all grooves.

(Assessment of Scratch)

After a first wafer was polished under the aforementioned condition, howmany streaks of 0.2 μm or larger are on a wafer was measured using awafer surface testing apparatus (WM2500) manufactured by TOPCONCORPORATION.

First Invention Example 1

A reactor was charged with 35 parts by weight of toluene diisocyanate(manufactured by Mitsui Takeda Chemicals, Inc., a mixture of toluene 2,4-diisocyanate/toluene 2,6-diisocyanate=80/20), 15.75 parts by weight of4,4′-dicyclohexylmethane diisocyanate, 44.3 parts by weight ofpolytetramethylene glycol A (manufactured by Mitsubishi Chemical Co.,Ltd., a number average molecular weight 650), and 4.95 parts by weightof 1,3-butylene glycol (manufactured by Nacalai Tesque, Inc.), and themixture was heated and stirred at 80° C. for 120 minutes to obtain anisocyanate-terminal prepolymer A (NCO wt %: 11.6 wt %).

Separately, a reactor was charged with 31.9 parts by weight of toluenediisocyanate (manufactured by Mitsui Takeda Chemicals, Inc., a mixtureof toluene 2, 4-diisocyanate/toluene 2, 6-diisocyanate=80/20), 8.5 partsby weight of 4,4′-dicyclohexylmethane diisocyanate, 53.9 parts by weightof polytetramethylene glycol B (manufactured by Mitsubishi Chemical Co.,Ltd., a number average molecular weight 1000), and 5.7 parts by weightof diethylene glycol (manufactured by Mitsubishi Chemical Co., Ltd.),and the mixture was heated and stirred at 80° C. for 120 minutes toobtain an isocyanate-terminal prepolymer B (NCO wt %: 9.2 wt %).

And, a reactor was charged with 45 parts by weight of anisocyanate-terminal prepolymer A, 55 parts by weight of anisocyanate-terminal prepolymer B, and 6 parts by weight of asilicone-based nonionic surfactant L5340 (manufactured by NihonunicaCorporation) (4.38% by weight in a polyurethane resin), and atemperature was adjusted at 80° C. Polytetramethylene glycolA/polytetramethylene glycol B=40/60 (wt %). Thereafter, stirring wasperformed vigorously at a rotation number of 900 rpm for about 4 minutesusing a stirring wing so that pores were taken into a reaction system.31 parts by weight of 4,4′-methylenebis(o-chloroaniline) (manufacturedby Ihara Chemical Industry Co., Ltd., Ihara Cureamine MT) which had beenmelted at 120° C. in advance was added thereto. After stirring wascontinued for about 1 minute, the reaction solution was poured into apan-type open mold. At a timepoint at which flowability of this reactionsolution was lost, it was placed into an oven, and post-cured at 110° C.for 6 hours to obtain a polyurethane resin foam block. This polyurethaneresin foam was sliced using a band saw-type slicer (manufactured byFecken) to obtain a polyurethane resin foam sheet. Then, this sheet wassurface-buffed to a predetermined thickness using a buffing machine(manufactured by Amitec Corporation) to obtain a sheet with an adjustedthickness precision (sheet thickness: 1.27 mm). This buffing-treatedsheet was punched into a predetermined diameter (61 cm), and a sheetsurface was subjected to concentric groove processing at a groove widthof 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm toprepare a polishing layer. Thereafter, a cushion material (cushionlayer) obtained by impregnating a commercially available non-wovenfabric with polyurethane was laminated on a back of the polishing layerto prepare a polishing pad.

Example 2

A reactor was charged with 60 parts by weight of an isocyanate-terminalprepolymer A, 40 parts by weight of an isocyanate-terminal prepolymer B,and 6 parts by weight of a silicone-based nonionic surfactant L5340(manufactured by Nihonunica Corporation) (4.35% by weight in apolyurethane resin), a temperature was adjusted at 80° C.Polytetramethylene glycol A/polytetramethylene glycol B=55/45 (wt %).Thereafter, stirring was performed vigorously at a rotation number of900 rpm for about 4 minutes using a stirring wing so that pores weretaken into a reaction system. 32 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd, Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Example 3

A reactor was charged with 70 parts by weight of an isocyanate-terminalprepolymer A, 30 parts by weight of an isocyanate-terminal prepolymer B,and 6 parts by weight of a silicone-based nonionic surfactant L5340(manufactured by Nihonunica Corporation) (4.32% by weight in apolyurethane resin), and a temperature was adjusted at 80° C.Polytetramethylene glycol A/polytetramethylene glycol B=65/35 (wt %).Thereafter, stirring was performed vigorously at a rotation number of900 rpm for about 4 minutes using a stirring wing so that pores aretaken into a reaction system. 32.8 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Example 4

A reactor was charged with 70 parts by weight of an isocyanate terminalprepolymer A, 30 parts by weight of an isocyanate-terminal prepolymer Band 6 parts by weight of a silicone-based nonionic surfactant L5340(manufactured by Nihonunica Corporation) (4.32 parts by weight in apolyurethane resin), and a temperature was adjusted at 80° C.Polytetramethylene glycol A/polytetramethylene glycol B=65/35 (wt %).Thereafter, stirring was performed vigorously at a rotation number of900 rpm for about 4 minutes using a stirring wing so that pores weretaken into a reaction system. 25.9 parts by weight of Ethacure 300(manufactured by Albemarle Corporation, a mixture of3,5-bis(methylthio)-2,6-toluenediamine and3,5-bis(methylthio)-2,4-toluenediamine) which had been adjusted at atemperature of 70° C. in advance was added thereto. Thereafter,according to the same manner as that of Example 1, a polishing pad wasprepared.

Comparative Example 1

A reactor was charged with 50 parts by weight of diisocyanate(manufactured by Mitsui Takeda Chemicals, Inc., a mixture of toluene2,4-diisocyanate/toluene 2, 6-diisocyanate=80/20), 15.75 parts by weightof 4,4′-dicyclohexylmethane diisocyanate, 44.3 parts by weight ofpolytetramethylene glycol (manufactured by Mitsubishi Chemical Co.,Ltd., a number average molecular weight 650), and 4.95 parts by weightof 1,3-butylene glycol (manufactured by Nacalai Tesque, Inc.), and themixture was heated and stirred at 80° C. for 120 minutes to obtain anisocyanate-terminal prepolymer C(NCO wt %: 16.1 wt %).

A reactor was charged with 100 parts by weight of an isocyanate-terminalprepolymer C, and 6 parts by weight of a silicone-based nonionicsurfactant L5340 (manufactured by Nihonunica Corporation) (3.88% byweight in a polyurethane resin), and a temperature was adjusted at 80°C. Thereafter, stirring was performed vigorously at a rotation number of900 rpm for about 4 minutes using a stirring wing so that pores weretaken into a reaction system. 48.5 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Comparative Example 2

A reactor was charged with 100 parts by weight of an isocyanate-terminalprepolymer B and 10 parts by weight of a silicone-based nonionicsurfactant L5340 (manufactured by Nihonunica Corporation) (7.34% byweight in a polyurethane resin), and a temperature was adjusted at 80°C. Thereafter, stirring was performed vigorously at a rotation number of900 rpm for about 4 minutes using a stirring wing so that pores weretaken into a reaction system. 26.2 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Comparative Example 3

A reactor was charged with 100 parts by weight of an isocyanate-terminalprepolymer B, and 3 parts by weight of a silicone-based nonionicsurfactant SH-192 (manufactured by Toray Dow Corning Silicone Co., Ltd.)(2.32% by weight in a polyurethane resin), and a temperature wasadjusted at 80° C. Thereafter, stirring was performed vigorously at arotation number of 900 rpm for about 4 minutes using a stirring wing sothat pores were taken into a reaction system. 26.2 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Using polishing pads obtained in Examples and Comparative Examples, apolishing test was performed to assess polishing property. Results areshown in Table 1.

TABLE 1 NCO Tensile Average Initial Polishing wt % breaking Tensile cellHard- polishing rate after Abrasion Dressing (average extension strengthdiameter Specific ness rate 10 hours amount speed Scratch value) (%)(MPa) (μm) gravity (degree) (Å/min) (Å/min) (Å) (μm/min) Clogging(number) Example 1 10.28 87.7 19 51 0.8 57 2350 2300 2550 7.7 ∘ 5Example 2 10.64 66.5 19.7 52 0.8 60 2380 2250 2250 7.5 ∘ 4 Example 310.88 50 20.8 50 0.8 62 2420 2320 2300 8.2 ∘ 5 Example 4 10.88 56.1 21.249 0.8 61 2320 2300 2250 8.1 ∘ 5 Comparative 16.1 15 20.3 53 0.8 75 21502100 2100 18.3 ∘ 19 Example 1 Comparative 9.2 148.9 17.7 53 0.77 42 22001750 3650 4.8 Δ 5 Example 2 Comparative 9.2 162 24.3 52 0.86 54 21001530 3100 4.1 x 4 Example 3

From results of Table 1, it is seen that, by using a polyurethane resinfoam having a tensile breaking extension of 25 to 120% as a material fora polishing layer, a polishing pad which hardly generates a scratch in apolishing object and is excellent in planarization property is obtained.In addition, it is seen that, in the polishing pad of the invention, apolishing rate is hardly reduced even when continuously used for a longperiod of time.

Second Invention Example 1

A reactor was charged with 35 parts by weight of a toluene diisocyanate(manufactured by Mitsui Takeda Chemicals, Inc., a mixture of toluene 2,4-diisocyanate/toluene 2, 6-diisocyanate=80/20), 15.75 parts by weightof 4,4′-dicyclohexylmethane diisocyanate, 44.3 parts by weight ofpolytetramethylene glycol (manufactured by Mitsubishi Chemical Co.,Ltd., a number average molecular weight 650), and 4.95 parts by weightof 1,3-butylene glycol (manufactured by Nacalai Tesque, Inc.), and themixture was heated and stirred at 80° C. for 120 minutes to obtain anisocyanate-terminal prepolymer A (NCO wt %: 11.6 wt %).

And, a reactor was charged with 100 parts by weight of anisocyanate-terminal prepolymer A, and 20 parts by weight of asilicone-based nonionic surfactant L5340 (manufactured by NihonunicaCorporation) (13% by weight in a polyurethane resin), and a temperaturewas adjusted at 80° C. Thereafter, stirring was performed vigorously ata rotation number of 900 rpm for about 4 minutes using a stirring wingso that pores were taken into a reaction system. 34 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. After stirring was continued for about 1minute, the reaction solution was poured into a pan-type open mold. At atimepoint at which flowability of this reaction solution was lost, thesolution was placed into an oven, and post-cured at 110° C. for 6 hoursto obtain a polyurethane resin foam block. This polyurethane resin foamblock was sliced using a band saw-type slicer (manufactured by Fecken)to obtain a polyurethane resin foam sheet. Then, this sheet wassurface-buffed to a predetermined thickness using a buffing machine(manufactured by Amitec Corporation) to obtain a sheet with an adjustedthickness precision (sheet thickness: 1.27 mm). This buff-treated sheetwas punched out into a predetermined diameter (61 cm), and a sheetsurface was subjected to concentric groove processing at a groove widthof 0.25 mm, a groove pitch of 1.50 mm and a groove depth of 0.40 mmusing a groove processing machine (manufactured by Toho Koki Co., Ltd.)to prepare a polishing layer. Thereafter, a cushion material (cushionlayer) obtained by impregnating a commercially available non-wovenfabric with polyurethane was laminated on a back of the polishing layerto prepare a polishing pad.

Example 2

According to the same manner as that of Example 1 except that 28 partsby weight of Ethacure 300 (manufactured by Albemarle Corporation, amixture of 3,5-bis(methylthio)-2,6-toluenediamine and3,5-bis(methylthio)-2,4-toluenediamine) was used in place of 34 parts byweight of 4,4′-methylenebis(o-chloroaniline) in Example 1, a polishingpad was prepared.

Example 3

According to the same manner as that of Example 1 except that an amountof a silicone-based nonionic surfactant L5340 was changed from 20 partsby weight to 15 parts by weight in Example 1, a polishing pad wasprepared.

Example 4

A reactor was charged with 35 parts by weight of toluene diisocyanate(manufactured by Mitsui Takeda Chemicals, Inc., a mixture of toluene 2,4-diisocyanate/toluene 2, 6-diisocyanate=80/20), 15.75 parts by weightof 4,4′-dicyclohexylmethane diisocyanate, 44.5 parts by weight ofpolyester polyol (number average molecular weight 650) obtained bypolycondensing adipic acid and diethylene glycol at 150° C., and 4.95parts by weight of 1,3-butylene glycol (manufactured by Nacalai Tesque,Inc.), and the mixture was heated and stirred at 80° C. for 120 minutesto obtain an isocyanate-terminal prepolymer B (NCO wt %: 11.5 wt %).

According to the same manner as that of Example 1 except that 100 partsby weight of an isocyanate-terminal prepolymer B was used in place of100 parts by weight of an isocyanate-terminal prepolymer A in Example 1,a polishing pad was prepared.

Comparative Example 1

According to the same manner as that of Example 1 except that an amountof a silicone-based nonionic surfactant L5340 was changed from 20 partsby weight to 5 parts by weight in Example 1, a polishing pad wasprepared.

Comparative Example 2

According to the same manner as that of Example 1 except that an amountof a silicone-based nonionic surfactant L5340 was changed from 20 partsby weight to 40 parts by weight in Example 1, a polishing pad wasprepared.

Comparative Example 3

A reactor was charged with 32.1 parts by weight of a toluenediisocyanate (manufactured by Mitsui Takeda Chemicals, Inc., a mixtureof toluene 2, 4-diisocyanate/toluene 2, 6-diisocyanate=80/20), 8.5 partsby weight of 4,4′-dicyclohexylmethane diisocyanate, 54.3 parts by weightof polytetramethylene glycol (manufactured by Mitsubishi Chemical Co.,Ltd., a number average molecular weight 1000), and 4.9 parts by weightof 1,3-butylene glycol (manufactured by Nacalai Tesque, Inc.), and themixture was heated and stirred at 80° C. for 120 minutes to obtain anisocyanate-terminal prepolymer C(NCO wt %: 9.1 wt %).

According to the same manner as that of Example 1 except that 100 partsby weight of an isocyanate-terminal prepolymer C was used in place of100 parts by weight of an isocyanate-terminal prepolymer A, and anamount of 4,4′-methylenebis(o-chloroaniline) was changed from 34 partsby weight to 26 parts by weight in Example 1, a polishing pad wasprepared.

Using polishing pads obtained in Examples and Comparative Examples, apolishing test was performed to assess polishing property. Results areshown in Table 2.

TABLE 2 Tensile Initial Polishing Average cell Askar D Tensile breakingpolishing rate after 10 Abrasion Surfactant diameter Specific hardnessstrength extension rate hours amount Scratch (wt %) (μm) gravity(degree) (MPa) (%) (Å/min) (Å/min) (Å) (number) Example 1 13.0 51 0.7856 16.9 60 2790 2810 2150 3 Example 2 13.5 50 0.77 55 15.9 68 2890 28502050 4 Example 3 10.1 51 0.76 58 17.3 55 2950 2970 2220 3 Example 4 13.051 0.75 61 19.3 75 3050 3000 2100 5 Comparative 3.6 55 0.95 71 25.5 222050 1750 2300 23 Example 1 Comparative 23.0 50 0.7 46 14.8 135 19801520 3700 6 Example 2 Comparative 13.7 51 0.73 42 13.2 141 2030 16103850 7 Example 3

As apparent from results of Table 2, by using a hydrophobichigh-molecular-weight polyol having a number average molecular weight of500 to 850 as a polyol component, and adding 10 to 20% by weight of asilicone-based nonionic surfactant having no hydroxy group to apolyurethane resin foam, a polishing pad which has a high polishing rateand is excellent in planarization property can be obtained. Thepolishing pad can suppress generation of scratch on a wafer.

Third Invention Example 1

A reactor was charged with 35 parts by weight of toluene diisocyanate(manufactured by Mitsui Takeda Chemicals, Inc., a mixture of toluene 2,4-diisocyanate/toluene 2, 6-diisocyanate=80/20), 15.75 parts by weightof 4,4′-dicyclohexylmethane diisocyanate, 44.3 parts by weight ofpolytetramethylene glycol (manufactured by Mitsubishi Chemical, Co.,Ltd., a number average molecular weight 650), and 4.95 parts by weightof 1,3-butylene glycol (manufactured by Nacalai Tesque, Inc.), and themixture was heated and stirred at 80° C. for 120 minutes to obtain anisocyanate-terminal prepolymer A (NCO wt %: 11.6 wt %).

Separately, a reactor was charged with 31.9 parts by weight of toluenediisocyanate (manufactured by Mitsui Takeda Chemicals, Inc., a mixtureof toluene 2, 4-diisocyanate/toluene 2, 6-diisocyanate=80/20), 8.5 partsby weight of 4,4′-dicyclohexylmethane diisocyanate, 53.9 parts by weightof polytetramethylene glycol (manufactured by Mitsubishi Chemical. Co.,Ltd., a number average molecular weight 1000), and 5.7 parts by weightof diethylene glycol (manufactured by Mitsubishi Chemical Co., Ltd.),and the mixture was heated and stirred at 80° C. for 120 minutes toobtain an isocyanate-terminal prepolymer B (NCO wt %: 9.2 wt %).

And, a reactor was charged with 35 parts by weight of anisocyanate-terminal prepolymer A, 65 parts by weight of anisocyanate-terminal prepolymer B, and 10 parts by weight of asilicone-based nonionic surfactant L5340 (manufactured by NihonunicaCorporation) (7.19% by weight in a polyurethane resin), and atemperature was adjusted at 80° C. Polytetramethylene glycolA/polytetramethylene glycol B=30/70 (wt %). Thereafter, stirring wasperformed vigorously at a rotation number of 900 rpm for about 4 minutesusing a stirring wing so that pores were taken into a reaction system.29 parts by weight of 4,4′-methylenebis(o-chloroaniline) (manufacturedby Ihara Chemical Industry Co., Ltd., Ihara Cureamine MT) which had beenmelted at 120° C. in advance was added thereto. After stirring wascontinued for about 1 minute, the reaction solution was poured into apan-type open mold. At a timepoint at which flowability of this reactionsolution was lost, the solution was placed into an oven, and post-curedat 110° C. for 6 hours to obtain a polyurethane resin foam block. Thispolyurethane resin foam block was sliced using a band saw-type slicer(manufactured by Fecken) to obtain a polyurethane resin foam sheet.Then, this sheet was surface-buffed to a predetermined thickness using abuffing machine (manufactured by Amitec Corporation) to obtain a sheetwith an adjusted thickness precision (sheet thickness: 1.27 mm). Thisbath-treated sheet was punched out into a predetermined diameter (61cm), and a sheet surface was subjected to concentric groove processingat a groove width of 0.25 mm, a groove pitch of 1.50 mm and a groovedepth of 0.40 mm using a groove processing machine (manufactured by TohoKoki Co., Ltd.) to prepare a polishing layer. Thereafter, a cushionmaterial (cushion layer) obtained by impregnating a commerciallyavailable non-woven fabric with polyurethane was laminated on a back ofthe polishing layer to prepare a polishing pad.

Example 2

According to the same manner as that of Example 1 except that 23 partsby weight of Ethacure 300 (manufactured by Albemarle Corporation, amixture of 3,5-bis(methylthio)-2,6-toluene diamine and3,5-bis(methylthio)-2,4-toluenediamine) was used in place of 29 parts byweight of 4,4′-methylenebis(o-chloroaniline) in Example 1, a polishingpad was prepared.

Example 3

A reactor was charged with 25 parts by weight of an isocyanate-terminalprepolymer A, 75 parts by weight of an isocyanate-terminal prepolymer B,and 6 parts by weight of a silicone-based nonionic surfactant L5340(manufactured by Nihonunica Corporation) (4.48% by weight in apolyurethane resin), and a temperature was adjusted at 80° C.Polytetramethylene glycol A/polytetramethylene glycol B=21/79 (wt %).Thereafter, stirring was performed vigorously at a rotation number of900 rpm for about 4 minutes using a stirring wing so that pores weretaken into a reaction system. 28 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Comparative Example 1

A reactor was charged with 100 parts by weight of an isocyanate-terminalprepolymer A, and 20 parts by weight of a silicone-based nonionicsurfactant L5340 (manufactured by Nihonunica Corporation) (12.9% byweight in a polyurethane resin), and a temperature was adjusted at 80°C. Thereafter, stirring was performed vigorously at a rotation number of900 rpm for about 4 minutes using a stirring wing so that pores weretaken into a reaction system. 35 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Comparative Example 2

A reactor was charged with 100 parts by weight of an isocyanate-terminalprepolymer B, and 6 parts by weight of a silicone-based nonionicsurfactant L5340 (manufactured by Nihonunica Corporation) (4.54% byweight in a polyurethane resin), and a temperature was adjusted at 80°C. Thereafter, stirring was performed vigorously at a rotation number of900 rpm for about 4 minutes using a stirring wing so that pores weretaken into a reaction system. 26.2 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Comparative Example 3

A reactor was charged with 100 parts by weight of an isocyanate-terminalprepolymer B, and 3 parts by weight of a silicone-based nonionicsurfactant SH-192 (manufactured by Toray Dow Corning Silicone Co., Ltd.)(2.32% by weight in a polyurethane resin), and a temperature wasadjusted at 80° C. Thereafter, stirring was performed vigorously at arotation number of 900 rpm for about 4 minutes using a stirring wing sothat pores were taken into a reaction system. 26.2 parts by weight of4,4′-methylenebis(o-chloroaniline) (manufactured by Ihara ChemicalIndustry Co., Ltd., Ihara Cureamine MT) which had been melted at 120° C.in advance was added thereto. Thereafter, according to the same manneras that of Example 1, a polishing pad was prepared.

Using polishing pads obtained in Examples and Comparative Examples, apolishing test was performed to assess polishing property. Results areshown in Table 3. In the case of Comparative Example 1, a groove on apad surface was lost by abrasion 8 hours after polishing.

TABLE 3 Average Tensile Initial Polishing Average cell Askar D Tensilebreaking polishing rate after Dressing Surfactant NCO diameter Specifichardness strength extension rate 10 hours speed (wt %) (wt %) (μm)gravity (degree) (MPa) (%) (Å/min) (Å/min) (μm/min) Clogging Example 17.19 10 51 0.82 53 23 141 2300 2250 7.5 ∘ Example 2 7.52 10 50 0.83 5422.1 129 2400 2310 7.2 ∘ Example 3 4.48 9.8 51 0.8 53 22.3 145 2350 22806.9 ∘ Comparative 12.90 11.6 52 0.55 42 19.2 54 2200 — 23.3 — Example 1Comparative 4.54 9.2 53 0.7 41 16.3 155 2150 1350 4.8 x Example 2Comparative 2.32 9.2 53 0.92 56 23.8 181 1900 1430 3.2 x Example 3

From results of Table 3, by using a polyurethane resin foam having anAskar D hardness of 45 to 55 degree, a specific gravity of 0.8 to 0.86,and a tensile breaking extension of 120 to 150%, a polishing pad can beobtained in which abrasive grains and polishing swarf are hardly cloggedin a groove during polishing, and a polishing rate is hardly reducedeven when continuously used for a long period of time.

1. A polishing pad comprising a polyurethane resin foam having a fine cell, and containing a polishing layer having a depression and protrusion structure on a polishing surface, wherein the polyurethane resin foam has an Askar D hardness of 45 to 55 degree, a specific gravity of 0.8 to 0.86, and a tensile breaking extension of 120 to 150%.
 2. The polishing pad according to claim 1, wherein the polyurethane resin foam is a reaction cured body of one or two or more kinds of isocyanate-terminal prepolymers containing a high-molecular-weight polyol component and an isocyanate component, and a chain extender, and a NCO wt % (in the case of two or more blends, average NCO wt %) of the isocyanate-terminal prepolymer is 9.3 to 10.5% by weight.
 3. The polishing pad according to claim 2, wherein the high-molecular-weight polyol component is a high-molecular-weight polyol A having a number average molecular weight of 500 to 850 and a high-molecular-weight polyol B having a number average molecular weight of 900 to 1500, and its content ratio is A/B=5/95 to 35/65 (wt %).
 4. The polishing pad according to claim 1, wherein the polyurethane resin foam has a tensile strength of 15 to 25 MPa.
 5. The polishing pad according to claim 2, wherein the chain extender is aromatic diamine.
 6. The polishing pad according to claim 5, wherein the aromatic diamine is 3,5-bis(methylthio)-2,4-toluenediamine and/or 3,5-bis(methylthio)-2,6-toluenediamine.
 7. The polishing pad according to claim 2, wherein the isocyanate component is aromatic diisocyanate and cycloaliphatic diisocyanate.
 8. The polishing pad according to claim 7, wherein the aromatic diisocyanate is toluene diisocyanate, and the cycloaliphatic diisocyanate is dicyclohexylmethane diisocyanate.
 9. The polishing pad according to claim 1, wherein the polyurethane resin foam contains a silicone-based nonionic surfactant having no hydroxy group at 0.05 to 10% by weight.
 10. The polishing pad according to claim 1, wherein a dressing speed is 5 to 10 μm/min. 